Furthermore, the conditions in Proposition REF  also implies that only routes with the minimum accumulated travel time are used, a property known as the Wardrop equilibrium principle [1]}. To see this implication, we define the set of route vectors from node \(i\)  to destination node \(s(j)\)  as follows:
\(\mathcal {P}(i, s(j)) = \left\lbrace u\in \lbrace 0, 1\rbrace ^{n_l}\left|\begin{aligned} &[Eu]_i=1, [Eu]_{s(j)}=-1,\\&[Eu]_k=0, \forall k\ne i, s(j).\end{aligned}\right.\right\rbrace .\) 
